There are 24 12-letter words that end with 'oning'.
Note: These 24 12-letter words that end with 'oning' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words end with ioning, ooning, soning, toning, roning, honing, poning, boning, eoning, doning, goning, zoning, koning, coning, moning, loning, noning, yoning.
6-letter words end with 'oning' (5)